1. Field of the Invention
The present invention relates generally to leveling devices for tractor hitch linkages and more specifically to locking and adjusting attachments for such mechanisms.
2. Description of the Prior Art
In the trailing arm implement hitch link systems generally used with modern agricultural tractors it is customary to provide a telescoping link mechanism by which the basic attitude of the trailing arm link may be adjusted according to the desires of the use of the tractor, responsive to varying soil and other use conditions. With the advent of enclosed cab constructions in modern agricultural tractors it has become desireable to provide means for the farmer to effect this adjustment in the attitude of his trailing linkage without leaving the cab. Such in-cab adjustment controls generally comprise a handle or crank mounted within the cab and connected through shafting having appropriate degrees of freedom to accommodate movements of the trailing hitch linkage with respect to the cab. The shafting generally serves as an input to some sort of a gear drive mechanism for running a telescoping link upwardly and downwardly to pivotally move the trailing hitch link of the tractor. Since during agricultural use in working soil, such as in plowing, significant loads are imposed upon the outboard end of the trailing link tending to move it away from the position to which it is adjusted. It has been found desireable to lock the adjusting mechanisms in their final adjusted position. When the adjustment device input member, i.e., the crank or hand wheel, is mounted in the tractor cab, attempts have been made to effect this lock by positioning a mechanical lock at the wheel or crank. Unfortunately this has been found to be less than satisfactory because the loads transferred back up the linkage from the tractor trailing hitch link are extremely high so that the durability of the hand wheel and operative shafting to which it is attached has been less than optimal.